Inductor topologies with substantial common-mode and differential-mode inductance

ABSTRACT

An inductor includes a core that has a window. The core includes a first core member and a second core member. A first winding is coupled to the first core member and a second winding is coupled to the second core member. A floating center leg is coupled between, but not attached to, the first and second core members. The floating center leg is conductively enabling flux flow between the first core member and the second core member.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending application Ser. No.11/533,992, filed on Sep. 21, 2006, incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to vehicle and non-vehicle electronic andelectrical systems and components. More particularly, the presentinvention is related to inductor topologies for common-mode anddifferential-mode filtering circuits and the like.

BACKGROUND OF THE INVENTION

A variety of power converters are used throughout industry. Powerconverters are often utilized in electronic circuits for direct current(DC) or alternate current (AC) conversion to supply power to electricmotors. Such conversion is performed on hybrid electric vehicles, fandrives, washing machines, refrigerators, and other various machines andequipment to improve efficiency and performance, as well as to minimizenoise.

Certain electronic circuits exhibit high switching speeds. At highswitching speed, the electronic circuits generate common-mode (CM) anddifferential-mode (DM) electromagnetic interference (EMI) noises. Thus,CM and DM filters are incorporated to remove such noise. Thetheoretically simplest filter topologies include capacitors andinductors that are without mutual-couplings between windings. However,in actual implementation, the inductors are normally with mutuallycoupled windings to minimize inductor size. Depending on the couplingpolarity to the inductors and the number of inductors used, the CM or DMnoises can be effectively blocked. Traditionally, a first inductor isused to filter CM noises and a second inductor is used to filter DMnoises. A single traditional inductor is not effective in simultaneouslyfiltering both CM and DM noises, due to the structure thereof.

There is a desire to further reduce the circuit size, cost, complexity,and weight associated with CM and DM inductor filtering. Thus, there isa need for an improved technique of providing CM and DM inductorfiltering.

SUMMARY OF THE INVENTION

In one embodiment of the present invention an inductor is provided thatincludes a core with a window. The core includes a first core member anda second core member. A first winding is coupled to the first coremember and a second winding is coupled to the second core member. One ormore cross-member(s) are coupled at least partially across and areconductively enabling flux flow between the first core member and thesecond core member.

In another embodiment of the present invention an electronic circuit isprovided that includes an input terminal, an inductor, and an outputterminal. The inductor is coupled to the input terminal and has only asingle inductive core. The inductor is coupled to filter bothcommon-mode noise and differential-mode noise. The output terminal iscoupled to and receives filtered common-mode and differential-modecurrent from the inductor.

The embodiments of the present invention provide several advantages. Oneadvantage provided by an embodiment of the present invention is acircuit having a single inductor that provides both common-mode anddifferential-mode filtering of electromagnetic interference noises.

The present invention is versatile in that it provides configurationsthat may be utilized and varied among a diverse range of applications,electronic circuits, and industries.

In addition, the present invention reduces the size, weight, andcomplexity of an electromagnetic interference filtering circuit and assuch the costs associated therewith.

The present invention itself, together with further objects andattendant advantages, will be best understood by reference to thefollowing detailed description, taken in conjunction with theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this invention reference should nowbe had to the embodiments illustrated in greater detail in theaccompanying figures and described below by way of examples of theinvention wherein:

FIG. 1 is a schematic view of a traditional electronic circuitincorporating common-mode and differential-mode filtering with inductorshaving single-coupled windings;

FIG. 2 is a schematic view of a traditional electronic circuitincorporating common-mode and differential-mode filtering with inductorshaving dual-coupled windings;

FIG. 3 is a side view of a traditional inductor having a single windowand a single winding;

FIG. 4 is a side view of another traditional inductor a pair of windowsand a single winding;

FIG. 5 is a side view of another traditional inductor having a singlewindow and a pair of windings;

FIG. 6 is a sample electronic circuit incorporating a dual-modefiltering inductor in accordance with an embodiment of the presentinvention;

FIG. 7A is a side magnetic flux flow representation of a dual-modefiltering inductor in accordance with an embodiment of the presentinvention;

FIG. 7B is a schematic view of a magnetic equivalent circuit of thedual-mode filtering inductor described with respect to FIG. 7A.

FIG. 8 is a perspective view of a dual-mode filtering inductor inaccordance with an embodiment of the present invention;

FIG. 9 is a side view of another dual-mode filtering inductorincorporating a single non-wound center leg in accordance with anotherembodiment of the present invention;

FIG. 10 is a side schematic view of a magnetic equivalent circuit of thedual-mode filtering inductor of FIG. 9;

FIG. 11 is a side view of another dual-mode filtering inductorincorporating a core having a split center leg in accordance withanother embodiment of the present invention;

FIG. 12 is a side view of another dual-mode filtering inductorincorporating a core surrounded and floating center leg in accordancewith another embodiment of the present invention;

FIG. 13 is a side view of another dual-mode filtering inductor having anouter flux flow enabling shell in accordance with another embodiment ofthe present invention; and

FIG. 14 is a side view of another dual-mode filtering inductor havingcore dividing center member in accordance with another embodiment of thepresent invention.

DETAILED DESCRIPTION

In the following described FIGS. 1 and 2 typical common-mode (CM) anddifferential-mode (DM) filter topologies are shown for the reduction ofelectromagnetic interference (EMI) noise emission. FIG. 1 illustrates asimple filter topology that includes capacitors and inductors withoutmutually coupled windings. FIG. 2 illustrates a filter topology withinductors that have mutually coupled windings.

Referring now to FIG. 1, a schematic view of a traditional electroniccircuit 10 that incorporates CM and DM filtering, with inductors 12 thathave single-coupled windings, is shown. The circuit 10 includes an EMIsource circuit 16 and a pair of inductor-based filtering circuits,namely, a DM filtering circuit 18, and a CM filtering circuit 20.

The EMI source circuit 16 has a CM source 22, which represents CM EMInoise generated by EMI circuit 16, and a pair of DM sources 24, 26,which represent DM EMI noise generated by EMI circuit 16. The CM source22 has a CM terminal 28 and a ground terminal 30. The EMI source circuitmay be in the form of a power source, a load, or a combination thereof.The DM sources 24, 26 have positive DM terminals 32 and negative DMterminals 34. Impedance between the CM source 22 and the DM sources 24,26 is shown and represented as a first impedance Z₁. The impedance Z₁ iscoupled between the CM terminal 28 and a DM terminal 36, which is inturn coupled between the DM sources 24, 26. Impedances between the DMsources 24, 26 and the DM filtering circuit 18 are shown andrepresented, respectively, as a second impedance Z₂ and a thirdimpedance Z₃. The EMI circuit 16 has a terminal A and a terminal B,which are coupled to the impedances Z₂ and Z₃, respectively.

The DM filtering circuit 18 includes a DM capacitor C_(x) and a DMinductor L_(x). The DM capacitor C_(x) is coupled to and across theterminals A and B and in parallel to the DM sources 24, 26. The DMinductor L_(x) has a single winding that is coupled in series with thesecond impedance Z₂ and post the DM capacitor C_(x). The DM filteringcircuit 18 has DM terminals C and D that are coupled to the DM inductorL_(x) and to the terminal B and the DM capacitor C_(x).

The CM filtering circuit 20 includes a pair of CM capacitors C_(y1) andC_(y2) and a pair of CM inductors L_(y1) and L_(y2). The CM capacitorsC_(y1) and C_(y2) are coupled in series with each other and are coupledin parallel with the DM capacitor C_(x). Each of the CM capacitorsC_(y1) and C_(y2) is coupled to either the DM terminal C or the DMterminal D and to ground. The first CM inductor L_(y1) is coupled to theDM terminal C and to the first CM capacitor C_(y1), on a first end 40,and to a CM terminal E, on a second end 42. The second CM inductorL_(y2) is coupled to the DM terminal D and to the second CM capacitorC_(y2), on a first end 44, and to a CM terminal F, on a second end 46.The CM terminals E and F may be input terminals or output terminals andmay be coupled to a load, a power source, or a combination thereof. Thelocation of the DM filter 18 and the CM filter 20 may be swapped orinterchanged. In other words, the CM filter 20 may be directly connectedto the circuit 16 and the DM filter 18 may be connected between the CMfilter 20 and the terminals E, F.

Referring now to FIG. 2, a schematic view of a traditional electroniccircuit 10′ that incorporates CM and DM filtering, with inductors 50that have dual-coupled windings, is shown. The electronic circuit 10′ issimilar to the electronic circuit 10. However, the single winding DMinductor L_(x) is replaced with a dual-winding DM inductor L_(x)′ andthe DM filtering circuit 18′ is configured as such. The inductor L_(x)′has a first differential inductor terminal 52 that is coupled to theterminal A, a second differential inductor terminal 54 that is coupledto the DM terminal B, a third differential inductor terminal 56 that iscoupled to the DM terminal C, and a fourth differential inductorterminal 58 that is coupled to the terminal D. The first terminal 52 andthe third terminal 56 are associated with a first differential winding60. The second terminal 54 and the fourth terminal 58 are associatedwith a seconding differential winding 62. Also, the CM inductors L_(y1)and L_(y2) are replaced with a single dual-winding CM inductor L_(y)′and the CM filtering circuit 20′ is configured as such. The CM inductorL_(y)′ has a first common winding 63 that is coupled between theterminals C and E and a second common winding 65 that is coupled betweenthe terminals D and F. Terminals 67 and 69 of the CM inductor L_(y)′ arecoupled to the DM terminals C and D, respectively. The electroniccircuit 10′ also includes a load circuit 51 with DM load impedancesZ_(DM) and CM load impedances Z_(CM). Similarly, the location of the DMfilter 18 and the CM filter 20 may be interchanged. In other words, theCM filter 20 may be connected to the circuit 16 and the DM filter 18 maybe connected between the CM filter 20 and the terminals E, F.

Referring now to FIGS. 1 and 2, in which CM and DM noise conduction isshown. CM noise is conducted directly from the CM source 22 to theterminals E and F on all lines, or through and inward from highestpotential and lowest potential branches, of the electronic circuits 10and 10′. The conduction of the CM noise is represented by the CM noiselines 64. DM noise is conducted in a current loop like fashion from thenegative or lower potential points in the electronic circuits 10 and 10′to the positive or higher potential points in the electronic circuits 10and 10′. The conduction of the DM noise is represented by the DM noiselines 66.

Although the combined sizes of inductors L_(x)′ plus L_(y)′ are smallerin size than the sum of inductors L_(x), L_(y1), and L_(y2), they aresimilar in that they are each only effective in blocking either CM or DMnoises. The coupling polarity of the mutual winding inductors determinesthe filtering characteristics of that inductor or whether the inductoris a CM or DM filtering inductor.

Referring now also to FIGS. 3-5, in which side views of traditionalinductors are shown. FIGS. 3-5 are herein included as illustratedexamples along with the following explanations associated therewith thatprovides reasons for which traditional inductors are incapable ofexhibiting both CM and DM filtering characteristics. In FIGS. 3 aninductor 70 that has a continuous core 71 having a single window 72 anda single winding 74 is shown. In FIG. 4 an inductor 75 that has acontinuous core 76 having two windows 78 and a single winding 80 isshown. The structures of the inductors 70 and 75 of FIGS. 3 and 4provide only DM filtering. The structures are incapable of blocking CMnoises since they have only a single winding. On the other hand, thedual-winding inductor 82 of FIG. 5 can be coupled to perform as eitheran effective CM or a DM filtering device, but not simultaneously. Notealso that the presence of multiple windings does not imply the abilityto block both DM and CM noises. Dual-winding configurations of theembodiments of the present invention are provided below that exhibitboth DM and CM noise filtering characteristics.

The dual-winding inductor 82 includes terminals c, d, e, and f and mayserve as a two-terminal DM inductor or as a four-terminal DM inductor.To serve as a two-terminal DM inductor, the inductor terminals d and eare connected together, while the inductor terminals c and f serve asthe external terminals. To serve as a four-terminal DM inductor, theinductor terminals c, d, e, and f are mapped, for example, to theterminals A, D, C, and B, respectively, of FIG. 2. Under thisarrangement, the DM current induces superimposed magneto-motive forces(mmfs) with high core flux and inductance. On the other hand, the CMcurrent through the windings 84 of the dual-winding inductor 82 inducesmutually canceling mmfs, therefore, with low actual flux and inductance.

To perform as a CM inductor, the dual-winding inductor 82 is configuredand serves as a CM choke. In comparison with the above four-terminal DMinductor approach, the polarity of one winding of the dual-windinginductor is reversed. For example, the inductor terminals d and f may beswapped to couple terminals B and D, respectively. Under thisarrangement, the dual-winding inductor 82 exhibits high CM inductancebut low DM impedance.

The present invention overcomes the limitations of traditional inductorapproaches and is described in detail below.

In each of the following figures, the same reference numerals are usedto refer to the same components. The present invention may apply toautomotive, aeronautical., nautical, and railway applications, as wellas to other applications in which substantial CM and DM filtering isdesired simultaneously. The present invention may be applied incommercial and non-commercial settings. The present invention may beapplied in appliances, in trailers, off-highway equipment, in auxiliaryequipment, in communication systems, and in a variety of otherapplications or settings,

Also, a variety of other embodiments are contemplated having differentcombinations of the below described features of the present invention,having features other than those described herein, or even lacking oneor more of those features. As such, it is understood that the inventioncan be carried out in various other suitable modes.

In the following description, various operating parameters andcomponents are described for one constructed embodiment. These specificparameters and components are included as examples and are not meant tobe limiting.

Referring now to FIG. 6, a sample electronic circuit 100 incorporating adual-mode filtering inductor 102 in accordance with an embodiment of thepresent invention is shown. The electronic circuit 100 includes an EMIsource circuit 104, a dual-mode filtering circuit 106, and terminals E′and F′, which may perform as output terminals and be coupled to one ormore drivers 110 and, respective one or more motors 112 (only one driverand motor are shown), as shown. The terminals E and F may, in additionor in the alternative to be coupled to a load, or be coupled to a powersource. Also, the terminals E and F may be used as input terminals,depending upon the application. Note that the arrangement, coupling, andconfiguration of the components of the electronic circuit 100 isprovided only as an example, an infinite number of other electricalcircuit arrangements, couplings, and configurations may be formedutilizing a dual-mode filtering inductor. Although the electroniccircuit is shown in the form of a DC dual-filtered drive circuit, and assuch the dual-mode inductor 102 is described in respect thereto, thedual-mode inductor 102 may be utilized and incorporated into otherelectronic circuits known in the art that have a need for DM and CMfiltering. Also, an inductor symbol is provided in FIG. 6 to representthe use of a dual-mode filtering inductor. The provided symbol does notrefer to one particular dual-mode filtering inductor, but rathersignifies that any one of the dual-mode filtering inductors describedherein or devised via the teachings herein may be utilized in theelectronic circuit 100.

The EMI circuit 104 includes a CM noise source 116, which represents theCM noise generated by the EMI circuit 104. The CM source 116 has asupply terminal 120 and a ground terminal 124. The supply terminal 120is coupled in series with a first impedance Z₁′. The ground terminal 124is coupled to the ground 125. The first impedance Z₁′ has firstimpedance terminals 126 and 128. The first impedance terminal 126 iscoupled to the supply terminal 120. The first impedance terminal 128 iscoupled to a pair of DM noise sources 130, 132, which represent the DMnoise conducted in the EMI circuit 104. The first DM source 130 hasfirst DM terminals 134 and 136. The first DM terminal 136 is coupled tothe first impedance terminal 128. The second DM source 132 has second DMterminals 138 and 140. The second DM terminal 138 is coupled to thefirst impedance terminal 128. The first DM terminal 134 is coupled to asource terminal A′ through impedance Z2. The second DM terminal 140 iscoupled to a source terminal B′ through impedance Z3.

A second impedance Z2′ and a third impedance Z3′ are coupled to the DMsources 130, 132. The second impedance Z2′ has second impedanceterminals 142 and 144. The third impedance Z3′ has third impedanceterminals 146 and 148. The second impedance terminal 142 is coupled tothe first DM source terminal 134. The third impedance terminal 146 iscoupled to the second DM source terminal 140.

The dual-mode filtering circuit 106 includes CM and DM capacitors andthe dual-mode inductor 102. A differential capacitor C_(x)′ is coupledin parallel with the DM sources 130, 132 and between the secondimpedance terminal 144 and the third impedance terminal 148 on theterminals A′ and B′. A pair of CM capacitors C_(y1)′ and C_(y2)′ arecoupled in series with each other and combined in parallel to the DMcapacitor C_(x)′. The first CM capacitor C_(y1)′ is coupled between theterminal A′ and ground 125. The second CM capacitor C_(y2)′ is coupledbetween ground 125 and the terminal B′.

The dual-mode inductor 102 has and/or is coupled to inductor terminalss, u, t, and v. The inductor terminals s and u are coupled to theterminals A′ and B′, respectively. The inductor terminals t and v arecoupled to the electronic circuit terminals E′ and F′. Terminals E′ andF′ may perform as input or output terminals, depending upon theapplication.

In the following FIGS. 7A and 7B, inductor topologies andrepresentations are provided for the example inductors of FIGS. 8-14.

Referring now to FIGS. 7A and 7B, a side magnetic flux flowrepresentation of a dual-mode inductor and a side schematic view of amagnetic equivalent circuit thereof are shown. The dual-mode inductorhas a core 150 with wound core members 151, 152 and lateral members 153,154. A pair of windings 155, 156 are wound on the wound core members151, 152, respectively. A pair of cross flux flow members 157, 158 arecoupled between diagonally opposite ends of the wound core members. Thewindings 155, 156 have terminals s′, t′, u′, and v′, which may be mappedto terminals s, t, u, and v of FIG. 6, respectively.

With two windings and two cross-members, the dual-mode inductor providessix magnetic internal flux paths P_(A), P_(B), P_(C), P_(D), P_(E), andP_(F) having associated magnetic flux therein, represented anddesignated by Φ_(A), Φ_(B), Φ_(C), Φ_(D), Φ_(E), and Φ_(F). The firstcore member 151 performs as flux path P_(A) and has flux Φ_(A), thesecond core member 152 performs as flux path P_(B) and has flux Φ_(B),the first lateral member 153 performs as flux path P_(C) and has fluxΦ_(C), the second lateral member 154 performs as flux path P_(D) and hasflux Φ_(D), the first cross-member 157 performs as flux path P_(E) andhas flux Φ_(E), and the second cross-member 158 performs as flux pathP_(F) and has flux Φ_(F). FIG. 7B shows the equivalent magnetic circuitfor the dual-mode inductor, where the magneto-motive forces (mmfs) aremodeled as equivalent voltage sources and the core reluctances aremodeled as resistances. The equivalent voltage sources are approximatelyequal to the product of the number of turns of the windings on the coremember of concern and the current through that winding. The number ofturns of the windings, for the dual-mode inductor, are represented by N₁and N₂ and the currents are represented by I₁ and I₂. Each of the coremembers 151, 152, 153, 154 and the cross-members 157, 158 has anassociated reluctance R_(A), R_(B), R_(C), R_(D), R_(E), and R_(F).

The flux through each branch or member in the dual-mode inductor can becalculated by known circuit theories. The below equations are providedassuming that the dual-mode inductor is symmetrical, such that thenumber of windings N₁ and N₂ are equal, the reluctance R_(A) is equal tothe reluctance R_(B), the reluctance R_(C) is equal to the reluctanceR_(D), and the reluctance R_(E) is equal to the reluctance R_(F). X andY component current variables I_(X) and I_(Y) are defined based oncombinations of winding currents I₁ and I₂ and are provided by equations1-4.

$\begin{matrix}{I_{X} = \frac{I_{1} + I_{2}}{2}} & (1) \\{I_{Y} = \frac{I_{1} + I_{2}}{2}} & (2) \\{{I_{1} = {I_{X} + I_{Y}}}} & (3) \\{I_{2} = {I_{X} - I_{Y}}} & (4)\end{matrix}$

When only the X flux current component exists, flux Φ_(A)flux Φ_(B),flux Φ_(C), and flux Φ_(D) are equal, and flux Φ_(E) and flux Φ_(F) areequal to zero. As such, flux Φ_(X) is provided by equation 5.

$\begin{matrix}{\Phi_{X} = \frac{{NI}_{X}}{R_{A} + R_{C}}} & (5)\end{matrix}$

From equation 5 the inductance L_(X) can be determined by equation 6.

$\begin{matrix}{L_{X} = {\frac{N\; \Phi_{X}}{I_{X}} = \frac{N^{2}}{R_{A} + R_{C}}}} & (6)\end{matrix}$

On the other hand, when only the Y flux current component exists, fluxΦ_(A), the inverse of flux Φ_(B), flux Φ_(E), and flux Φ_(F) are equal,and flux Φ_(C) and flux Φ_(D) are equal to zero. As such, flux Φ_(F) isprovided by equation 7 and the inductance L_(Y) is provided by equation8.

$\begin{matrix}{\Phi_{Y} = \frac{{NI}_{Y}}{R_{A} + R_{E}}} & (7) \\{L_{Y} = {\frac{N\; \Phi_{Y}}{I_{Y}} = \frac{N^{2}}{R_{A} + A_{E}}}} & (8)\end{matrix}$

Equations 6 and 8 show that the inductances L_(X) and L_(Y) can bedetermined independently. Also, if the currents include the X and Ycomponents, according to equations 3 and 4, the windings 155, 156 aresized to handle the sum, or the difference, of both components.Similarly, by combining equations 5 and 7, the core paths P_(A) andP_(B) are sized to handle the sum, or the difference, of the X and Yflux components. The core paths P_(C) and P_(D) are sized to handle theX-component. The core paths P_(E) and P_(F) are sized to pass theY-component.

In certain cases, some of the core members may have zero or infinitereluctance. For example, if the reluctance R_(C) and the reluctanceR_(D) are equal to zero, the topology of the dual-mode inductor becomesas shown in FIGS. 9 and 10.

Note that in the following FIGS. 8-14 dual-mode filtering inductors areprovided that having a particular number of members, windings,cross-members, and windows, these are examples only. Other combinationsmay be formed having varying numbers of members, windings,cross-members, and windows.

Referring now to FIG. 8, a perspective view of a dual-mode filteringinductor 160 in accordance with an embodiment of the present inventionis shown. Although many of the features of the inductor 160 are belowdescribed with “input” and “output” designations, these are relativeterms and depending upon the application, the stated designations may bereversed. For example, the winding terminals of the inductor that arccoupled to receive input current determines which winding terminals areinput terminals and which are output terminals and, similarly, whichcore member ends are input ends and which are output ends.

The dual-mode inductor 160 has a core 162 with a window 164. In general,the core 162 includes multiple legs or members 166. For the embodimentshown, the core 162 has a first wound core member 168 and a second woundcore member 170. The first core member 168 and the second core member170 are coupled to each other via a pair of cross-members 172, 174. Thecross-members 172, 174 are coupled across the window 164 and provide anincreased number of magnetic flux flow paths over traditional inductors.

The first core member 168 has a first conductive element winding 176 anda first core input end 167 and a first core output end 169 on eitherside of the first winding 176. The second core member 170 has a secondconductive element winding 178 and a second core input end 171 and asecond core output end 173 on either side of the second winding 178. Thewindings 176, 178 have terminals s″, t″, u″, and v″, which may be mappedto terminals s, t, u, and v of FIG. 6, respectively.

A pair of lateral core members 180, 181 is coupled between the woundcore members 168 and 170. The lateral members 180, 181 are integrallyformed as part of the core 162, along with the wound core members 168and 170. The first lateral member 180 is coupled to and between thefirst output end 167 and the second input end 171. The second lateralmember 181 is coupled to and between the first input end 169 and thesecond output end 173. Each of the lateral members 180 and 181 has abreak 182 such that the core 162 is split. The breaks 182 in the lateralmembers 180, 181 form the four lateral elements M1, M2, M3, and M4. Theelements M1 and M2 are coupled to the first core member 168 and thesecond core member 170. Similarly, the elements M3 and M4 are alsocoupled to the first core member 168 and the second core member 170. Afirst gap G1 exists between the elements M1 and M2. A second gap G2exists between the elements M3 and M4. The gaps G1 and G2 provide lowpermittivity to prevent current saturation at full load. The gaps G1 andG2 or other additional gaps may be of various sizes and shapes, and maybe filled with other materials to adjust the effective permeability ofthe core or other characteristics. A few other inductor dual-modefiltering examples having different gapped configurations are providedbelow with respect to FIGS. 11-14.

The cross-members 172 and 174 may have a variety of associated sizes,shapes, and configurations. The first cross-member 172 is coupled to thediagonally opposite ends 167 and 173 via the elements M1 and M4. Thesecond cross-member 174 is coupled to the diagonally opposite ends 169and 171 via the elements M2 and M3.

The core 162, the core members 168 and 170, the elements M1-M4, and thecross-members 172 and 174, and the windings 176, 178 may be formed ofmaterials commonly associated with an inductor. The core 162 may beformed of iron, iron powder, ferrite, or other suitable core materialsor material combinations. The windings 176, 178 may be formed of copper,aluminum, gold, silver, or other suitable winding materials or materialcombinations.

Referring now to FIGS. 9 and 10, a side view of another dual-modefiltering inductor 190 that incorporates a single non-wound center leg192 and a side schematic view of the magnetic equivalent circuit thereofin accordance with another embodiment of the present invention is shown.The dual-mode inductor 190 represents a special case of the dual-modeinductor 160 with zero impedance along the paths P_(C) and P_(D). It hasa core 194 with a first core wound member 196, a second core woundmember 198, and lateral members 200. The impedance of the lateralmembers 200 may be divided and lumped together respectively with that ofcore members 194 and 198. The non-wound center leg 192 has windows 203and 205 on either side thereof. The first core wound member flux Φ_(A)and associated reluctance R_(A), the second core wound member flux Φ_(B)and associated reluctance R_(B), and the center member flux Φ_(E/F) andassociated reluctance R_(E/F) are shown in FIG. 10.

When the Y-component current I_(Y) is equal to zero, then theX-component flux Φ_(X) and the inductance L_(X) are as provided inequations 9 and 10 where the flux Φ_(E/F) is equal to zero.

$\begin{matrix}{\Phi_{X} = {\frac{{NI}_{X}}{R_{A}} = {\Phi_{A} = \Phi_{B}}}} & (9) \\{L_{X} = {\frac{N\; \Phi_{X}}{I_{X}} = \frac{N^{2}}{R_{A}}}} & (10)\end{matrix}$

On the other hand, when the X-component current I_(X) is equal to zero,the Y-component flux Φ_(Y) and the inductance L_(Y) are as provided inequations 11 and 12.

$\begin{matrix}{\Phi_{Y} = {\frac{\Phi_{ElF}}{2} = {\frac{{NI}_{Y}}{R_{A} + {2R_{C}}} = {\Phi_{A} = {- \Phi_{B}}}}}} & (11) \\{L_{Y} = {\frac{N\; \Phi_{Y}}{I_{Y}} = {\frac{N^{2}}{R_{A} + {2R_{C}}} \leq L_{X}}}} & (12)\end{matrix}$

The inductance L_(Y) equal or smaller than the inductance L_(X), and thecore path P_(E/F) is sized to accommodate the Y-component.

In the following FIGS. 11-14, additional example implementations ofdual-mode filtering inductors are provided. The X flux components andthe Y flux components are shown in each of FIGS. 11-14 for each of theassociated dual-mode filtering inductors. The X flux components areshown by the flow lines 206, respectively. The Y flux components areshown by the flow lines 208, respectively.

Referring now to FIG. 11, a side view of another dual-mode filteringinductor 210 that incorporates a continuous core 212 with a split centerleg 214 is shown in accordance with another embodiment of the presentinvention. The core 212 has wound core members 216, 218, lateral members220, and a single window 221. The center leg 214 is coupled between thelateral members 220 and has a first center element 222 and a secondcenter element 224. The center leg 214 also has a break 226 with anassociated gap G3 between the first center element 222 and the secondcenter element 224. The gap G3 may be filled with materials to adjustthe effective permeability of the core or other characteristics thereof.

Referring now to FIG. 12, a side view of another dual-mode filteringinductor 230 that incorporates a core 232 within a surrounded andfloating center leg 234 is shown in accordance with another embodimentof the present invention. The dual-mode inductor 230 also has acontinuous core with wound core members 236, 238 and lateral members240. The floating center leg 234 is coupled between, but is not attachedto the lateral members 240, and is within the window 241. A pair of gapsG4 and G5 exists between the longitudinal ends 242 of the floatingcenter leg 234 and the lateral members 240. Although a pair of gaps areshown along the center leg 234, any number of gaps may be incorporated.Also, gaps may be included along the core 232. In addition, the gaps maybe filled with materials to adjust the effective permeability of thecore or other characteristics thereof.

Referring now to FIG. 13, a side view of another dual-mode filteringinductor 250 that has an outer flux flow enabling shell 252 is shown inaccordance with another embodiment of the present invention. Thedual-mode inductor 250 includes a continuous core 254 with wound coremembers 256, 258 and lateral members 260. The shell 252 surrounds thecore 254. A pair of small gaps G6 and G7 exist between the lateralmembers 260 and the shell 252 and a pair of large gaps G8 and G9 existbetween the wound core members 256, 258 and the shell 252. Instead ofproviding additional flux paths via a center leg, the dual-mode inductor250 provides additional flux paths via the shell 252. Flux created bythe passage of current through the windings 270, 272 creates magneticflux that circulates through the wound core members 256, 258 and theshell 252, as shown. The Y flux components circulate over or across thesmall gaps G6 and G7. Similarly, the shell 252 may formed or consist ofmultiple sections with gaps therebetween. Again the gaps may be filledwith a variety of materials.

Referring now to FIG. 14, a side view of another dual-mode filteringinductor 280 that has a core dividing center member 282 in accordancewith another embodiment of the present invention is shown. The dual-modeinductor 280 includes a non-continuous core 284 that has wound coremembers 286, 288 and lateral members 290 with breaks 292, 294. Thecenter member 282 is isolated from or not in contact with the lateralmembers 290, divides the window 291, and is disposed within the gapsassociated with the breaks 292, 294. The center member 282 extendsbetween the lateral members 290 and is coupled between lateral elements296 of each lateral member 290. Gaps G10, G11, G12, and G13 existbetween each of the lateral elements 296 and the center member 282.

The present invention provides a multiple dual-mode filtering inductorsand associated electronic circuits for diverse applications. The statedinductors and circuits reduce the number of inductors needed to provideboth common-mode and differential-mode filtering.

While the invention has been described in connection with one or moreembodiments, it is to be understood that the specific mechanisms andtechniques which have been described are merely illustrative of theprinciples of the invention, numerous modifications may be made to themethods and apparatus described without departing from the spirit andscope of the invention as defined by the appended claims.

1. An inductor comprising: a core having a window and comprising; afirst core member; a second core member; and lateral core membersdisposed between said first and second core members a first windingcoupled to said first core member; a second winding coupled to saidsecond core member; and at least one floating center leg coupled betweenbut not attached to said core, said floating center leg conductivelyenabling flux flow between said first core member and said second coremember such that both common-mode noise and differential mode noise aresimultaneously filtered.
 2. An inductor as in claim 1 wherein said atleast floating center leg has at least one pair of gaps between saidfloating center leg and said core.
 3. An inductor as claimed in claim 2wherein said at least one pair of gaps is filled with a predeterminedmaterial.
 4. An inductor as in claim 1 wherein said core is a continuouscore.
 5. An inductor as in claim 1 wherein said at least one floatingcenter leg is a dividing member between said first core member and saidsecond core member.
 6. An inductor as in claim 5 wherein said corefurther comprises at least one break.
 7. An inductor as in claim 6wherein said at least one break is filled with a predetermined materialfor adjusting a permeability of said core.